This paper analyzed the Chaobai River Basin 1991 -2000 spatial and temporal evolution of precipitation data, using the same -rate amplifying method to handle precipitation data of each year for overall rotation. After each treatment, the total rainfall for each year is the 1991- 2000 average annual precipitation. Then based on GBHM (Geomorphology -Based Hydrological Model) model, we simulated the runoff of 10 years. The results show that in the same situation of total precipitation, spatial and temporal distribution of precipitation in 1994 is the most beneficial type for runoff, and its total runoff volume and peak flow reach maximums. The total runoff volume and peak flow in the 1999 type are minimums. The total runoff volume in the 1994 type is 3.88 times the total runoff volume in the 1999 type; the peak flow in the 1994 type is 35.87 times the peak flow in the 1999 type. Thus, with the same amount of precipitation, its spatial and temporal distribution has enormous impacts on the total runoff volume and peak flow.